Today, in most countries, women over a certain age (usually 40) are screened for breast cancer using X-ray mammography. If the results of the X-ray mammography present suspicious or potentially cancerous breast tissue, the patient is sent for a diagnostic workup. Alternatively, the patient can be sent for a diagnostic workup through other paths, such as the result of a physical examination in which the examining physician feels or otherwise identifies some abnormal feature (e.g., lump) in a patient's breast, or in circumstance in which the patient has an extremely high risk of cancer as determined through the patient's clinical, history, or other means.
In a diagnostic workup, the patient's breasts will be imaged with one of several imaging modalities, including X-ray mammography (digital or analog), MRI, or ultrasound, for the purposes of screening or evaluating for anatomical abnormalities in breast tissue including microcalcifications or masses in breast tissue, and various other lesions or abnormalities that are potentially cancerous. Newer techniques are also being developed for diagnostic purposes, including X-ray tomosynthesis, optical imaging, strain imaging, nuclear imaging, etc, which can be used to obtain diagnostic images of the patient's breast for evaluation by the physician determine whether a particular lesion in breast tissue is benign or malignant.
After reviewing a diagnostic image, if the physician believes that a lesion may be malignant, a biopsy will be performed to remove a piece of the lesion tissue for analysis. This process is assumed to be a “gold standard” for characterization of benign or malignant tissue. However, it is preferable to minimize the number of biopsies that are performed for various reasons. For instance, a biopsy procedure causes pain and scarring for the patient, and the long period of time between the time of the biopsy procedure and the time the results are provided to the patient (usually at least a few days), the patient may be become severely stressed in anticipation of potentially obtaining negative results. On the other hand, biopsy procedures enable physicians to accurately diagnose a large percentage of patients with breast cancer. Thus, there is some trade-off or balance between sensitivity and specificity that is typically maintained.
In the field of medical imaging, although various imaging modalities and systems can be used for generating diagnostic images of anatomical structures for purposes of screening and evaluating medical conditions, with respect to breast cancer detection, each diagnostic imaging modality has its own advantages and disadvantages, and the optimal choice of imaging modality may not be the same for every patient. Ideally, the imaging modality for a given patient is selected to maximize sensitivity and specificity for the patient. For each patient, there may be one or more “optimal” imaging modalities for such purpose. Unfortunately, due to cost, it is not possible to image every patient using multiple imaging modalities, and then choose which modality would provide the optimal balance between sensitivity and specificity.
The choice of diagnostic imaging modality is usually made by the referring physician based on a number of factors, including, for example, (i) availability and cost, (ii) comfort level and experience of the referring physician, or (ii) a physician's “gut feeling” as to which imaging modality would be optimal to obtain information for the patient. While the first factor is unavoidable, the second and third factors can lead to a sub-optimal choice of imaging modality for the individual patient.